First off that technician is totally wrong. Replacing the NAND flash on your iPad is not only a ridiculously hard and possibly really expensive thing to do, but unless you have a special kind of machine it won’t even work. As for your problem, what version of iOS is it on at the moment?

Do you have a friend that also has the original Xbox One? If so I’d first recommend seeing if the same thing happens when you use one of their power bricks, just to rule out the possibility of it being the Xbox itself. If that works, I’d recommend just replacing the power supply. Those can be really dangerous to work with, since they have capacities that could possibly cause serious damage if touched.

You decided to rush and damaged your phone. First: it doesn’t matter what specific cables were ripped since they would require some intense micro soldering skills to replace. Your best bet would be to purchase another display assembly, either via iFixit or another vendor. Second: you need to make sure you follow all the steps on a guide exactly or you risk causing serious damage to the phone. I assumed disconnecting the battery while doing an iPhone 6s screen replacement wasn’t necessary and I blew out the Backlight IC. Follow the guides exactly and you should be good to go, aside from the fact that you’ve probably damaged your phone other ways when you ripped it open instead of taking out the pentalobes. Also, while I understand your problem with the batteries you got from iFixit, your best bet for returns is probably iFixit customer service, not the forums.